To support NOAA Coral Reef Conservation Program (CRCP) long-term
goals for sustainable management and conservation of coral reef
ecosystems, towed-diver surveys (AKA towboard surveys) are
conducted by the Coral Reef Ecosystem Division (CRED) of the
NOAA Pacific Islands Fisheries Science Center (PIFSC) as part of
Pacific Reef Assessment and Monitoring Program (RAMP) Cruises.
14 towboard surveys (totaling 27.77 km in length) were conducted
at Wake in Pacific Remote Island Areas from 20110310 to 20110402
as part of RAMP Cruise HA1101. Towboard surveys are a good
method for obtaining a general description of large reef areas,
assessing the status of low-density populations of large-bodied
reef fish, large-scale disturbances (e.g., bleaching), general
distribution and abundance patterns of macro-invertebrates
(e.g., crown of thorns sea stars, giant clams), and for
assessing trends in these populations and metrics. A pair of
scuba divers (1 fish diver and 1 benthic diver) are towed 60 m
behind a small survey launch at a speed of 1-2 knots and a depth
of approximately 15 m. Each survey is 50 min long, covers about
2 km of habitat, and is divided into ten 5-minute survey
segments. The fish diver records, to the lowest possible taxon,
all large-bodied reef fishes (greater than 50 cm total length)
seen within 5 m either side and 10 m in front of the towboard.
Length of each individual is estimated to the nearest cm. The
fish towboard is also outfitted with a forward-facing digital
video camera to record the survey swath. The benthic diver
records percent cover of coral and macroalgae, estimates benthic
habitat type and complexity, and censuses a suite of benthic
macroinvertebrates including crown of thorns sea stars and sea
urchins. The benthic towboard is equipped with a downward-facing
digital still camera which images the benthos at 15-second
intervals. These images are analyzed for percent cover of coral,
algae, and other benthic components. Both towboards are equipped
with SEABIRD SBE-39 temperature/depth sensors set to record at
5-second intervals. Latitude and longitude of each survey track
is recorded at 15-second intervals using a Global Positioning
System (GPS) receiver onboard the tow boat. A layback algorithm
is applied to more accurately map the position of the divers
with respect to the reef environment. This algorithm calculates
the position of the divers based on the position of the tow boat
taking into account the length of the tow rope, the depth of the
divers, and the curvature of the survey track. This metadata
applies to the fish biomass observations.

Supplemental_Information:

Data collected: Species level abundance and length information
for coral reef fishes greater than 50 cm total length. Data is
linked to a geographic shapefile via DiveID or SegID. Abundance
and/or biomass data can be provided at the species or family
level.

Horizontal positions are specified in geographic coordinates, that is, latitude and longitude.
Latitudes are given to the nearest 0.0001.
Longitudes are given to the nearest 0.0001.
Latitude and longitude values are specified in Decimal Degrees.

The horizontal datum used is World Geodetic System 1984 (WGS84).
The ellipsoid used is Geodetic Reference System 80 (GRS80).
The semi-major axis of the ellipsoid used is 6378137.
The flattening of the ellipsoid used is 1/298.2572236.

The towboard survey involves a pair of scuba divers who are
towed 60 m behind a small boat at a constant speed (~1.5
knots). The towboard survey is typically 50-min long and
covers about 2 km of habitat, depending on the depth profile
of the divers. The survey is divided into ten 5-min segments.
During the survey, the fish diver records, to the lowest
possible taxon, large fishes observed within a survey swath 5
m to either side of the diver and 10 m in front the diver.

Although resource grade GPS units were used and a layback
model was applied to the survey tracks, the exact survey
positions were not physically marked and effort was not made
to re-visit exact same tracks.

The towboard surveys are completed in forereef, backreef, and
lagoon habitats. The minimum spatial resolution of the towboard
survey is the 5-minute survey segment which covers approximately
200 m. As such, these surveys are appropriate for broad estimates
but cannot be used for fine scale, site-level data analysis.

While every effort has been made to ensure that these data are
accurate and reliable within the limits of the current state of
the art, NOAA cannot assume liability for any damages caused by
errors or omissions in the data, nor as a result of the failure of
the data to function on a particular system. NOAA makes no
warranty, expressed or implied, nor does the fact of distribution
constitute such a warranty.